Method and apparatus for in-phase and quadrature imbalance correction in a frequency domain

Abstract

An apparatus and method for in-phase/quadrature (I/Q) imbalance correction in a transceiver. The apparatus includes an I/Q imbalance correction circuit and a correction coefficient generation circuit. The I/Q imbalance correction circuit is configured to modify I/Q data in a frequency domain using correction coefficients to generate corrected I/Q data. The correction coefficient generation circuit is configured to generate the correction coefficients for the I/Q imbalance correction circuit based on the I/Q data and reference data.

What is claimed is: 
     
       1. An apparatus for in-phase/quadrature (I/Q) imbalance correction in a transceiver, comprising:
 an analog mixer circuit configured to down-convert a received signal to a non-zero intermediate frequency; 
 an analog-to-digital converter (ADC) configured convert the down-converted received signal to I/Q data in a digital domain; 
 a first down-conversion circuit configured to down-convert the I/Q data to baseband for a signal of interest; 
 a second down-conversion circuit configured to down-convert the I/Q data to baseband for a mirror image of the signal of interest; 
 an I/Q imbalance correction circuit configured to modify the baseband I/Q data of the signal of interest in a frequency domain using correction coefficients to generate corrected I/Q data, wherein the I/Q imbalance correction circuit is configured to generate the corrected I/Q data based on the baseband I/Q data of the signal of interest and a complex conjugate of the baseband I/Q data of the mirror image of the signal of interest in a frequency domain; and 
 a correction coefficient generation circuit configured to generate the correction coefficients for the I/Q imbalance correction circuit based on the baseband I/Q data of the signal of interest and reference data. 
 
     
     
       2. The apparatus of  claim 1 , wherein the ADC is a radio frequency (RF) ADC configured to digitize the down-converted received signal over a frequency of the signal of interest and a frequency of the mirror image of the signal of interest. 
     
     
       3. The apparatus of  claim 1 , wherein the received signal is an orthogonal frequency division multiplex (OFDM) modulated signal and a cyclic prefix attached to an OFDM symbol is longer than an impulse response length of an I/Q imbalance channel. 
     
     
       4. The apparatus of  claim 1 , wherein the I/Q imbalance correction circuit is further configured to perform RF equalization. 
     
     
       5. The apparatus of  claim 1 , wherein the reference data is obtained from a pilot signal, a reference symbol, or a training sequence included in the received signal. 
     
     
       6. A method for in-phase/quadrature (I/Q) imbalance correction in a transceiver, comprising:
 down-converting a received signal to a non-zero intermediate frequency; 
 converting, by an analog-to-digital converter (ADC), the down-converted received signal to I/Q data in a digital domain; 
 down-converting the I/Q data to baseband for a signal of interest; 
 down-converting the I/Q data to baseband for a mirror image of the signal of interest; 
 generating correction coefficients based on the baseband I/Q data of the signal of interest and reference data; and 
 modifying the baseband I/Q data of the signal of interest in a frequency domain using the correction coefficients to generate corrected I/Q data, wherein the corrected I/Q data is generated based on the baseband I/Q data of the signal of interest and a complex conjugate of the baseband I/Q data of the mirror image of the signal of interest in a frequency domain. 
 
     
     
       7. The method of  claim 6 , wherein the ADC is a radio frequency (RF) ADC configured to digitize the down-converted received signal over a frequency of the signal of interest and a frequency of the mirror image of the signal of interest. 
     
     
       8. The method of  claim 6 , wherein the received signal is an orthogonal frequency division multiplex (OFDM) modulated signal and a cyclic prefix attached to an OFDM symbol is longer than an impulse response length of an I/Q imbalance channel. 
     
     
       9. The method of  claim 6 , further comprising performing RF equalization. 
     
     
       10. The method of  claim 6 , wherein the reference data is obtained from a pilot signal, a reference symbol, or a training sequence included in the received signal.